1. Field of the Invention
The present invention relates to a mechanism for movement of articles along a prefixed path, with the path preferably having an elliptical shape.
2. Description of the Prior Art
In many industrial systems and plants it is required that some articles are moved along a prefixed path, especially when assembling or treating products. For example, it is often necessary to transfer component parts, members and articles in general, between two predetermined positions of the system. For instance the assembled or finished products from a manufacturing line have to be moved from the assembly final station to a transporter which carries them to the quality control, store or shipping departments.
For the sake of simplicity, in the following specification reference will be expressly made to the transfer of a finished article from the assembling line (or island) to the conveying system which collects the manufactured articles (generally from various lines or islands) and transports the same to successive operating steps, although such an application is only an illustrative example, in no way considered limiting to the possible uses of the device according to the invention.
To this aim, according to a known solution, special transferring devices are used with an intermediate station, with the transferring devices comprising a trolley or the like, provided with grasping means and suitable provisions to move along a rail or guide generally extending crosswise with respect to the feed direction of the manufacturing line and/or the discharge conveyor.
Such a transferring device was found to be unsatisfactory for various reasons. First of all, the device has a considerable and permanent encumbrance, due to the presence of a track, and generally requires a special construction based on the features of the system, such as the distance between manufacturing line and transferring device.
Secondly, the performance of this type of device is rather poor. For example two grasping means (pliers or the like) are generally required, cantilevered on a support to obtain the translating motion and to place the article onto the trolley or take it therefrom, the transfer speed is low (of about 1 meter/second) and the sequence of the steps further increases the total transfer time. In addition, although the followed path (law of movement) can be theoretically programmed, in practice this is usually not economical. Additionally, the device may be noisy.
The use of a true robot has also been proposed, having an arm with four degrees of freedom and a grasping means at its end. However, such a solution, although providing reduced encumbrance and good flexibility both for applicability and possibilities of path, requires the use of a device which is undoubtedly exuberant in relation with the task to be performed, and consequently involves an inadequate use thereof, resulting in unnecessarily high costs.
An object of the present invention is to overcome the above-illustrated inconveniences and limitations of the known devices, and in particular to provide a self-supporting mechanism of simple construction, and consequently of low cost, which, at the same time provides for flexible usage which can be adapted to different situations, with the mechanism having reduced encumbrance and requiring no fixed installations for its operation. It has been realized that the various paths adopted in practice, as exemplified by the above cases, can be made to descend in almost all cases from an elliptical path, since varying the eccentricity from 0 to 1 provides paths which range from circular to rectilinear motion (harmonic or rectilinear, non uniform), as particular cases of the elliptical path.
Therefore, it is another object of the present invention to provide a mechanism which, being driven by only one driving means, is capable of moving the free end of an outermost arm along a path defined according to the general equation of an ellipse having its center corresponding with the support base, or more precisely, with the center of the ellipse corresponding to the pivoting axis of the first of a plurality of arms on the support base.